Unchokable centrifugal pump

ABSTRACT

A centrifugal pump having a single-blade rotor whose central suction mouth, remote from the driving shaft, is in alignment with the inlet opening, the inlet opening forming an annular collar which so projects into the inside of the rotor that the inner end of the rotor blade forms a narrow gap with the outer surface of the collar.

FIELD OF THE INVENTION

The present invention relates to a centrifugal pump having asingle-blade rotor whose central suction mouth, remote from the drivingshaft, is in alignment with the inlet opening of the pump chamber.

BACKGROUND OF THE INVENTION

Non-chokable pumps are often used for waste waters charged with solids.These non-chokable pumps have maximum efficiencies of approximately 50%,but in practical application the efficiency is below 40%. These lowefficiencies result in an overdimensioning of the driving motor. Sincein submersible motor-driven pumps the motor represents approximately 80%of the value of a pump, there is an increase in the investment costsrequired to deliver a predetermined quantity of liquid to a givenheight.

Non-chokable pumps also have the peculiarity that solids accumulate atthe center of the rotor and reduce the unobstructed flow passage, sothat the pump output is throttled. The pump itself does not becomeclogged, since the end face of the rotor is well away from the wall ofthe pump casing.

Rotors having an improved efficiency are single-channel rotors havingonly one blade. These rotors attain efficiencies of over 70% if they arespatially curved. Because of the spatial curvature, the rotors cannot beturned down to reach other operating points. A separate rotor istherefore required for each characteristic line and also its own modelin the foundry. Cylindrical rotors can be turned down and have aslightly lower efficiency than the spatially curved ones.

OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide animproved centrifugal pump which is of simple construction andmanufacture, and to a high degree unchokable.

SUMMARY OF THE INVENTION

This object is achieved according to the invention by providing theinlet opening so that it forms an annular collar which so projects intothe inside of the rotor that the inner end of the rotor blade forms anarrow gap with the outer surface of the collar.

Such a pump does not become choked, even by very troublesome solids inthe medium being delivered such as, for example, plastics, bags andpantyhose. The pump is therefore particularly efficient for waste watersof different kinds. Moreover, the cylindrical rotor of the pumpaccording to the invention can be turned down.

Particularly advantageously mounted in the pump chamber side wall havingthe inlet is an end plate forming the collar directly or via an insert.

Preferably according to the invention the insert forming the collar liesbush-fashion or sleeve-like at least in that zone of the inlet which isadjacent the rotor.

Also preferably according to the invention the end of the chamber sidewall adjacent the rotor forms, especially via an end plate, a spiralgroove which extends around the inlet and through which solidspenetrating between the rotor and the chamber side wall can be movedoutwards. Solids forcing themselves in between the lower edge of therotor and the chamber side wall are entrained by the spiral and moveradially outwards, so that the rotor spontaneously frees itself fromjammed solids.

It is of the greatest advantage if on the outside of the collar the endplate is adjoined by a coaxial toothed rim whose teeth are directedsubstantially radially. The effect of the radial teeth is that the solidmaterial does not endlessly corotate with the rotor, but is held back,so that the outwardly rotating spiral can develop its full action. Inthis way solids which have become looped around the front edge of therotor are also held back via the teeth and subjected to the action ofthe spiral. Lastly, the teeth can exert a comminuting action on certainsolids.

Preferably according to the invention that end face of the inner end ofthe rotor blade which is adjacent the bottom plate extends around abovethe toothed rim at a small distance. The spiral groove should adjoin theoutside of the toothed rim.

Also preferably according to the invention the width of the teeth andtherefore of the toothed rim is substantially equal to the width of theend face of the inner end of the rotor blade, and the rotor blade endhas a radius, so that the solids can be drawn in much more simply.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become morereadily apparent from the following description, reference being made tothe accompanying drawing in which:

FIG. 1 is an axial section through a detail of a first embodiment;

FIG. 2 is an axial section through a detail of a second embodiment;

FIG. 3 is a view showing the pump chamber side wall with toothed rim anda short inner zone of the spiral; and

FIG. 4 is a detail perspective view of the collar, toothed rim, spiraland inner end of the rotor blade.

SPECIFIC DESCRIPTION

A centrifugal pump has a pump casing 1 forming a pump chamber 2 in whicha rotor 3 is mounted. The rotor 3 is driven by an electric motor (notshown) via a shaft 4.

On the side remote from the shaft 4 and the electric motor the chamber 2is closed by a pump chamber side wall 5 which lies at a right angle tothe axis of the shaft 4 and forms a pump inlet 6 which lies coaxiallywith the shaft 4 and is therefore in alignment with the suction mouth ofthe rotor 3.

The rotor 3, which is cylindrical and can therefore be turned down, hasonly one single curved blade 7 whose inner end 7a-i.e., the end closerto the rotor axis 8-rotates very close to the edge of the inlet 6. Theinner edge of the inlet 6 forms an annular collar 9 which extends a fewmillimeters into the rotor 3 and therefore into the suction mouth of therotor 3, so that the collar 9 projects beyond the inner end 7a by a fewmillimeters. Preferably the collar 9 projects beyond the inner end 7a by2 to 5, preferably 2.5 to 3 millimeters.

Left between the outside of the collar 9 and the inside wall of theinner end 7a of the rotor blade is a gap 10 of only approximately afraction of a millimeter, the radial width S of the gap increasing withincreasing output.

The collar 9 can be directly formed by the pump chamber side wall 5(FIG. 1) in one piece therewith or by an end plate 11 or an insert 12attached to the end plate 11 (FIG. 2). The insert 12 can line the inlet6 as a bush or sleeve.

As FIG. 1 shows, on the inside of the pump chamber side wall 5 theinsert 6 is surrounded by a spiral groove 13 having in relation to thecirculating liquid a spiral direction A such that solids penetratingbetween the rotor blade and the chamber side wall are driven radiallyoutwards, as shown by the dot-dash line direction of flow 14 witharrows, shown in FIG. 4.

In the embodiment illustrated in FIGS. 2 to 4, disposed between thecollar 9 and the spiral groove 13 is a coaxial toothed rim 15 over whichend face 16 of the inner end of the rotor blade is disposed at a smalldistance, the width b of the toothed rim being substantially equal tothe width B of the end face 16. The teeth of the toothed rim 15 liessubstantially radially in relation to the rotor axis 8 -i.e., thestraight tooth flank lines of the teeth are disposed substantiallyradially.

Particularly advantageously the lower front end of the rotor blade frontside has a radius via which the fibrous substances are drawn in by therotor blade and forced to move outwards, due to the design of the endplate. The transition from the inner end 7a to the end face 16 istherefore rounded off, the rounding having the radius R.

I claim:
 1. A centrifugal pump comprising:a pump housing surrounding anaxis and formed with a pump chamber having a side wall defining an inletopening centered on said axis; an end plate ..received in a side wall ofsaid housing; a driving shaft axially aligned with said inlet opening; asingle-blade rotor having an inner end Juxtaposed with said end plateand a central suction mouth remote from the driving shaft in alignmentwith the inlet opening of the pump chamber; and an annular collarsurrounding said inlet opening and so projecting into the inside of therotor that an inner end of a rotor blade of said rotor forms a narrowgap with an outer surface of the collar, said outer surface beingprovided with a coaxial toothed rim having teeth directed substantiallyradially and disposed adjacent said end plate and spaced from said innerend of the rotor at a small distance, a width of the toothed rim (b)being substantially equal to a width (B) of the end face of the innerend of the rotor blade.
 2. The centrifugal pump defined in claim 1,further comprising: an end plate mounted in a side wall of said housingformed with the inlet opening, said end plate being formed with thecollar.
 3. The centrifugal pump defined in claim 1 wherein said endplate is formed directly with the collar.
 4. The centrifugal pumpdefined in claim 2 wherein said end plate is provided with an insertformed with said collar.
 5. The centrifugal pump defined in claim 4wherein the insert forming the collar is a sleeve disposed at least at azone of the inlet opening which is adjacent the rotor.
 6. Thecentrifugal pump defined in claim 1 wherein said housing has a chamberside wall adjacent the rotor formed with a spiral groove which extendsaround the inlet opening and via which solids penetrating between therotor and the chamber side wall are displaceable outwards.
 7. Thecentrifugal pump defined in claim 6 wherein said spiral groove is formedon an end plate mounted in said side wall.
 8. The centrifugal pumpdefined in claim 1 wherein a spiral groove is formed in said end plateadjoining an outside of the toothed rim.
 9. The centrifugal pump definedin claim 1 wherein an end face lower end of a front side of the rotorblade has a rounded portion having a radius (R) through which fibrousmaterials are drawn in.
 10. The centrifugal pump defined in claim 1wherein an end face lower end of a front side of the rotor blade has arounded portion having a radius (R) through which fibrous materials aredrawn in.
 11. A centrifugal pump comprising:a pump housing surroundingan axis and formed with a pump chamber having an inlet opening centeredon said axis; a driving shaft axially aligned with said inlet opening; asingle-blade rotor having a central suction mouth remote from thedriving shaft in alignment with the inlet opening of the pump chamber;and an annular collar surrounding said inlet opening and so projectinginto the inside of the rotor that an inner end of a rotor blade of saidrotor forms a narrow gap with an outer surface of the collar, said outersurface being provided with a coaxial toothed rim having teeth directedsubstantially radially.
 12. The centrifugal pump defined in claim 11wherein said rim is disposed adjacent an end plate received in a sidewall of said housing formed with said inlet opening.
 13. The centrifugalpump defined in claim 12 wherein an end face of an inner end of therotor blade which is adjacent the end plate extends around above thetoothed rim at a small distance therefrom.
 14. The centrifugal pumpdefined in claim 12 wherein a spiral groove is formed in said end plateadjoining an outside of the toothed rim.
 15. The centrifugal pumpdefined in claim 12 wherein a width (b) of the teeth and of the toothedrim is substantially equal to a width (B) of the end face of the innerend of the rotor blade.
 16. The centrifugal pump defined in claim 13wherein an end face lower end of a front side of the rotor blade has arounded portion having a radius (R) through which fibrous materials aredrawn in.